Pharmaceutical compositions

ABSTRACT

Compounds of formula (I) ##STR1## in which R 1  represents hydrogen, a C 1-6  aliphatic hydrocarbyl group or a C 1-4  aliphatic hydrocarbyl group substituted by a C 3-6  alicyclic hydrocarbyl group or by a phenyl group, which phenyl group is unsubstituted or substituted by a halogeno or C 1-3  halogenoalkyl group, R 2  represents hydrogen, R 3  represents hydrogen, a 5-or 6-membered ring aromatic heterocyclyl group containing one or two heteroatoms selected from nitrogen, oxygen and sulphur which is unsubstituted or substituted by a halogeno or C 1-3  halogenoalkyl group, or a group AR wherein A is a straight chain C 1-4  aliphatic hydrocarbyl group terminally substituted by R which is hydrogen, a phenyl group or a 5-or 6-membered ring aromatic heterocyclyl group containing one or two heteroatoms selected from nitrogen, oxygen and sulphur, which phenyl or heterocyclyl group R is unsubstituted or substituted by a halogeno or C 1-3  halogenoalkyl group, R 4  and R 5  each represent hydrogen or together represent an oxo group and R 6 , R 7  and R 8  each represent hydrogen, or R 4  represents hydrogen and two of R 5 , R 6 , R 7  and R 8  together represent the second bond of a double bond joining positions 4 and 5, 5 and 6 or 6 and 7 with the remaining two of R 5 , R 6 , R 7  and R 8  representing hydrogen, the compound optionally being in the form of a salt thereof formed with a physiologically acceptable inorganic or organic acid, are of value for the treatment of anxiety and in the improvement of learning ability and/or the reversal of amnesia.

This is a Rule 60 Division of application Ser. No. 08/290,752, filed 15,Aug. 1994, U.S. Pat. No. 5,476,867.

This invention relates to psychoactive compounds of value in thetreatment of anxiety and in the improvement of learning ability and thereversal of amnesia.

DESCRIPTION OF THE INVENTION

Accordingly the present invention comprises a compound of formula (I)##STR2## in which R₁ represents hydrogen, a C₁₋₆ aliphatic hydrocarbylgroup or a C₁₋₄ aliphatic hydrocarbyl group substituted by a C₃₋₆alicyclic hydrocarbyl group or by a phenyl group, which phenyl group isunsubstituted or substituted by a halogeno of C₁₋₃ halogenoalkyl group,R₂ represents hydrogen, R₃ represents hydrogen, a 5- or 6-membered ringaromatic heterocyclyl group containing one or two heteroatoms selectedfrom nitrogen, oxygen and sulphur which is unsubstituted or substitutedby a halogeno or C₁₋₃ halogenoalkyl group, or a group AR wherein A is astraight chain C₁₋₄ aliphatic hydrocarbyl group terminally substitutedby R which is hydrogen, a phenyl group or a 5- or 6-membered ringaromatic heterocyclyl group containing one or two heteroatoms selectedfrom nitrogen, oxygen and sulphur, which phenyl or heterocyclyl group Ris unsubstituted or substituted by a halogeno or C₁₋₃ halogenoalkylgroup, R₄ and R₅ each represent hydrogen or together represent an oxogroup and R₆, R₇ and R₈ each represent hydrogen, or R₄ representshydrogen and two of R₅, R₆, R₇ and R₈ together represent the second bondof a double bond joining positions 4 and 5, 5 and 6 or 6 and 7 with theremaining two of R₅, R₆, R₇ and R₈ representing hydrogen, the compoundoptionally being. in the form of a salt thereof formed with aphysiologically acceptable inorganic or organic acid, for use intherapy.

The invention further comprises the compounds per se of formula (I) asjust defined with the exception of the compound in which each of R₁ toR₈ is hydrogen, which has been described by Vasella (Helvetica ChimicaActa, 1977, 60, 1273-1293) as a compound produced in an investigation ofthe reactions of N-alkoxyalkyl nitrones.

The system of numbering used herein is based on that of thebenzo[d]isoxazole ring system as shown below ##STR3## The standardmethod is used for indicating stereochemistry in formula (I), i.e. athickened line represents a bond projecting upwardly from the plane ofthe paper. It will be seen that the compounds of the present inventiontherefore have cis stereochemistry with respect to the relativeorientation of the hydrogen atoms at positions 3a and 7a.

The group R₁ may be hydrogen but, if this is the case, it is preferredthat R₃ is other than hydrogen. However, R₁ is preferably a branched orespecially straight chain substituted or especially unsubstitutedaliphatic hydrocarbyl group. This monovalent aliphatic hydrocarbyl groupmay be unsaturated, especially by one double or triple bond,particularly when the group is unsubstituted, for example being apropargyl or especially an allyl group. Preferably, however, it issaturated, for example being a methyl, ethyl, n-propyl or isopropylgroup with the straight chain alkyl groups and especially methyl beingpreferred, although with some particular interest in ethyl and largergroups when it is substituted, particularly by phenyl. Where R₁ is analiphatic hydrocarbyl group substituted by an alicyclic hydrocarbylgroup or less preferably an unsubstituted or substituted phenyl group,the substituent group is conveniently terminally substituted on thealiphatic hydrocarbyl group. The alicyclic hydrocarbyl group ispreferably a cycloalkyl group such as cyclopropyl or cyclohexyl and thephenyl group is preferably unsubstituted although when it is substitutedthe preferences are as described hereinafter for substituted phenylgroups R₃. Examples of such substituted aliphatic hydrocarbyl groups R₁are cyclohexylmethyl and especially cyclopropylmethyl, and alsophenylmethyl and especially 2-phenylethyl.

The group R₂ is hydrogen. Although each of R₄ to R₈ may be hydrogen, thegroups R₄ and R₅ are preferably either together an oxo group or R₄ ishydrogen and R₅ together with R₆ is the second bond of a double bondjoining positions 4 and 5. Alternatively, when R₄ is hydrogen but R₅ andR₆ are not a bond, either R₆ and R₇ may be the second bond of a doublebond joining positions 5 and 6 or R₇ and R₈ may be the second bond of adouble bond joining positions 6 and 7. However, it is preferred that,where the one optional double bond in the six membered ring is present,it joins positions 4 and 5 so that R₇ and R₈ are usually each hydrogen.

A group R₃ which is hydrogen is of particular interest, especially whenR₄ and R₅ together are an oxo group. However groups R₃ of the form ARare also of interest, especially when R₄ is hydrogen and R₅ togetherwith R₆ is the second bond of a double bond and also when R₄ and R₅together are an oxo group. When R₃ is a group AR, R is preferably aphenyl group which, as indicated, may optionally be substituted by ahalogeno group, for example a bromo, chloro or especially a fluoro groupor more particularly a C₁₋₃ halogenoalkyl group, for example a propyl,ethyl or especially a methyl group substituted by one, two or especiallythree halogeno groups, particularly groups as just described. Thepreferred substituent is a CF₃ group, and in general substitution ispreferably at the meta position, although the particular preference isfor a phenyl group which is unsubstituted.

As indicated, R₃ itself or a group R in a group R₃ of the form AR mayalso be an aromatic heterocyclyl group. In general such heterocyclylgroups are of most interest as part of a group AR. In either instance,groups of interest are furyl, pyrrolyl, thienyl, pyridyl, oxazolyl,thiazolyl and pyrimidyl, the 5-membered ring systems being of particularinterest, such as thiazolyl, especially pyrrolyl, particularly thienyl,for example thien-2-yl, and most particularly furyl, for examplefur-2-yl. Such heterocyclyl groups may be substituted, the preferencesbeing as described for the substituted phenyl groups in a group AR butin general it is preferred that the heterocyclyl groups areunsubstituted.

The divalent aliphatic hydrocarbyl group A may be unsaturated,especially by one double or triple bond, for example being a --CH₂--C.tbd.C-- or especially a --CH₂ --CH═CH-- group. However, straightchain alkylene groups A of the form --(CH₂)_(n) -- wherein n is 1 to 4are of most interest, for example --CH₂ --, --CH₂ CH₂ -- and --CH₂ CH₂CH₂ --. The preferred chain length for A is 1 to 3 carbon atoms,especially 1 or 2 carbon atoms.

A group AR may thus conveniently be a C₁₋₄ alkyl group, for example anethyl or especially a methyl group substituted by a C₆ H₅ or CF₃. C₆ H₄group or, to a lesser extent, by a furyl or other unsubstituted aromaticheterocyclyl group as specified above. Groups AR of particular interestare benzyl and 2-phenylethyl and, to a lesser extent, the analoguesthereof containing a fur-3-yl or especially a fur-2-yl group in place ofthe phenyl group.

Examples of specific compounds according to the present invention arethose containing a combination of the preferences for R₁ to R₈ indicatedabove, for example the compounds in which

(1) R₁ is CH₃, R₂ is H, R₃ is C₆ H₅ CH₂, R₄ and R₅ are ═O, and R₆, R₇and R₈ are H (cis-3-benzyl-2-methyl-2,3,3a,4,5,6,7,7a-octahydrobenzo[d]isoxazol-4-one);

(2) is R₁ is CH₃, R₂ is H, R₃ is C₆ H₅ CH₂, R₄ is H, R₅ and R₆ are abond, and R₇ and R₈ are H(cis-3-benzyl-2-methyl-2,3,3a,6,7,7a-hexahydrobenzo [d]isoxazole);

(3) R₁ is CH₃, R₂ is H, R₃ is C₆ H₅ CH₂ CH₂, and R₄ R₅ are ═O, and R₆,R₇ and R₈ H (cis-2-methyl-3-(2-phenylethyl)-2,3,3a,4,5,6,7,7a-octahydrobenzo[d ]isoxazol-4-one);

(4) R₁ is CH₃, R₂ is H, R₃ is H, R₄ and R₅ are ═O, and R₆, R₇ and R₈ areH (cis-2-methyl -2,3,3a,4,5,6,7,7a-octahydrobenzo[d]isoxazol-4-one); and

(5) R₁ is CH₃, R₂ is H, R₃ is H, R₄ is H, R₅ and R₆ are a bond, and R₇and R₈ are H (cis-2-methyl-2,3,3a,6,7,7a-hexahydrobenzo[d]isoxazole).

Of these, compound (1) and especially compound (4) are of particularinterest.

As indicated, the compounds of formula (I) may exist in the form of anamine type salt formed with a physiologically acceptable inorganic ororganic acid. A preferred acid is hydrochloric acid but other acidswhich may be used include hydrobromic, sulphuric, nitric, phosphoric,isethionic, acetic, fumaric, maleic, salicylic, p-toluenesulphonic,tartaric, citric, lactobionic, formic, malonic, pantothenic, succinic,naphthalene-2-sulphonic, benzenesulphonic, methanesulphonic andethanesulphonic acid. In general, however, use of the free base ratherthan a salt is preferred.

Although the stereochemistry of the molecule is in part indicated informula (I), a group R₃ which is not hydrogen may adopt one of twoorientations relative to the two mutually cis hydrogen atoms atpositions 3a and 7a. It is preferred, however. that this group has thetrans configuration relative to these hydrogen atoms, i.e. the hydrogenatom R₂ and the hydrogen atoms at the 3a and 7a positions are similarlydisposed in the cis configuration. Thus, the preferred form of each ofthe specific compounds (1) to (3) hereinbefore may be identified ashaving the relative stereochemistry 3R*,3aS*, 7aS* (the lowest numberedposition, position 3, being assigned the R* configuration). Moreover, itwill be appreciated that the compounds according to the invention willbe resolvable into enantiomeric forms, one of which may be of particularvalue by virtue of its level of therapeutic activity and/or physicalproperties such as greater aqueous solubility, etc.

The compounds of formula (I) may be prepared by a number of alternativeroutes. In a first process a compound of formula (II) is reacted with acompound of formula (III) ##STR4## in which R₁ to R₈ are as defined forthe compound of formula (I). Such a process is particularly suited tothe preparation of compounds (I) in which R₁ is a substituted orunsubstituted aliphatic hydrocarbyl group and R₃ is a group AR. Thepreparation of compounds of formula (I) in which R₃ is hydrogen is moreconveniently effected through the formation of the compound of formula(III) in situ through the use of a compound of formula (IIIa),HN(R₁)-CH₃, which is then converted to the compound of formula (III)##STR5## through the use of tungstate catalysed oxidation of thesecondary amine (IIIa).

In a second process a compound of formula (II) as defined above isreacted with a compound of formula (IV) and a compound of formula (V)##STR6## in which R₁ and R₃ are as defined for the compound of formula(I), the compound of formula (V) often being in salt form. Such aprocess is of particular value as a route to compounds (I) in which oneor both of R₁ and R₃ is hydrogen.

It will be appreciated, however, that the compounds of formula (I) mayalso be prepared by modifications of these processes and by otheralternative processes which will be apparent from the chemical art.

The first mentioned process generally requires heating of the reactantstogether, for example at 70°-100° C. in a sealed tube under an inert gassuch as nitrogen for a period of 14 to 24 hours. As indicated, theN-oxide may alternatively be generated in situ by oxidation of thecorresponding secondary amine, for example with pertungstic acid, whenthe reaction may be effected at a lower temperature, for example at roomtemperature. The second mentioned process generally requires reaction ina suitable solvent, for example ethanol, at room temperature, forexample for a similar time period to the first mentioned process.

When the compound of formula (I) is in salt form, such salts may beprepared from the free base by treatment with the appropriate acid,either in a polar solvent such as water, if necessary with theapplication of heat, or more conveniently generating an acid such ashydrochloric acid in situ in a non-aqueous solvent, for example methanolas illustrated in Example 5.

The compounds of formula (I) are of value for the treatment of anxiety,being of particular interest for the treatment of anxiogenesis caused bywithdrawal from benzodiazepines such as diazepam as they exhibit crosstolerance with these benzodiazepines in comparison with buspirone, forexample, which does not. The compounds (I) are also of interest for thetreatment of anxiogenesis caused by abruptly ceasing administration ofdrugs of abuse and in particular nicotine, alcohol and cocaine.

The compounds of formula (I) are alternatively of value for use in theimprovement of learning and/or the reversal of amnesia, for examplearising from Alzheimer's disease or vascular dementias.

The dose rates required to achieve effective anxiolysis, improvement inlearning ability or reversal of amnesia will of course vary with themammal treated, the mammal's body weight, surface area, age and generalstate of health, but as a guide it may be stated that in human patientsa suitable dose for parenteral administration is in the range of 0.001ng/kg to 10 mg/kg, particularly 1 ng/kg to 1 mg/kg, and for oraladministration is in the range of 1 μg/kg to 10 mg/kg, particularly 10μg/kg to 1 mg/kg and especially 10 μg/kg to 100 μg/kg, and that othermammals may be treated on a similar mg/kg basis. Such doses may berepeated as desired, for example 2 to 3 times a day during the period oftreatment. Doses outside these ranges may also be given if appropriate.In general the improvement of learning ability and/or the reversal ofamnesia requires somewhat lower doses within the ranges given than thetreatment of anxiety.

Administration may be by mouth or, less usually, parenterally (includingsubcutaneously, intramuscularly and intravenously) or topically.

Whilst it is possible for the compound (I) to be administered alone itis preferable to present it in a pharmaceutical composition.Compositions of the present invention for medical use comprise one ormore of the active compounds (I) together with one or morepharmaceutically acceptable diluents or carriers and, optionally, othertherapeutic ingredients. The diluent(s) or carrier(s) should bepharmaceutically acceptable in the sense of being compatible with theother ingredients of the formulation and not deleterious to therecipient thereof.

Compositions include those suitable for oral, parenteral or topicaladministration. The formulations may conveniently be presented in unitdosage form and may be prepared by any of the methods well known in theart of pharmacy. In general, formulation includes the step of bringingthe active compound(s) (I) into association with a diluent or carrierand, where appropriate, one or more accessory ingredients. Usually, theformulations are prepared by bringing the active compound uniformly andintimately into association with a liquid or with a finely divided solidor with both and then, where appropriate, shaping the product intodesired formulations.

Compositions of the present invention suitable for oral administrationmay conveniently be presented as discrete units such as capsules,cachets, tablets or lozenges, each containing a predetermined amount ofthe active compound, for example as a powder or granules, or as asolution or a suspension in an aqueous liquid or non-aqueous liquid suchas a syrup, an elixir, an emulsion or a draught. The compound may alsobe presented as a bolus, electuary or paste.

A tablet may be made by compression or moulding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared bycompressing, in a suitable machine, the active compound in afree-flowing form such as a powder or granules, optionally mixed with abinder, lubricant, inert diluent, surface active or dispersing agent.Moulded tablets may be made by moulding, in a suitable machine, amixture of the powdered active compound with any suitable carrier.

A syrup may be made by adding the active compound to a concentrated,aqueous solution of a sugar, for example sucrose, to which may be addedany accessory ingredient. Such accessory ingredient(s) may includeflavourings, an agent to retard crystallisation of the sugar or an agentto increase the solubility of any other ingredient, such as a polyhydricalcohol, for example glycerol or sorbitol.

Compositions suitable for parental administration conveniently comprisea sterile aqueous preparation of the active compound which is preferablyisotonic with the blood of the recipient.

Other types of composition include aerosols and suppositories.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now described in more detail with reference to theaccompanying drawings, in which:

FIGS. 1 and 2 show the results of studies of a compound of the inventionon mice in the black: white test box;

FIG. 3 shows the results of studies of a compound of the invention onrat social interaction;

FIGS. 4 and 5 show the results of a compound of the invention on theanxiolytic profile over different periods of time;

FIG. 6 shows the results of studies to assess the ability tocross-tolerate with diazepam;

FIGS. 7 through 9 show the results of studies on the ability to inhibitbehavioral consequences of withdrawal from drugs of abuse;

FIGS. 10 through 16 show the results in the mouse habituation test todemonstrate improvement of learning ability and reversal ofscopolamine-induced amnesia.

EXAMPLES

The invention is illustrated by the following Examples. The designationrel-(3R*, 3aS*,7aS*) in the names of the compounds of Examples 1, 2, 3,5 and 6 indicates that the substituent at the 3 position is oppositelyorientated relative to the two cis hydrogen atoms at positions 3a and7a.

Example 1

Preparation of rel,(3R*,3aS*,7aS*)-3-benzyl-2-methyl-2,3,3a,4,5,6,7,7a-octahydrobenzo[d]isoxazol -4-one and substitutedderivatives thereof

(A)

In a dry sealed tube under N₂ were placedN-(2-phenylethylidene)methylamine N-oxide (2.0 g, 13.4 mmol) and2-cyclohexenone (5 ml). The reagents were stirred at 100° C. for 15hours. Unreacted 2-cyclohexenone was removed by Kugelrohr distillationto yield the crude product as a viscous brown oil (K100%). The crudeproduct was purified by flash chromatography on silica gel (Sorbsil C60,60A) using 60:40 v/v petroleum ether (fraction of bp 40°-60° C):ethylacetate as the solvent system to give the unsubstituted title compoundas an orange oil (2.48 g. 75%) , υ_(max) (film) 2944, 2872, 1709, 1455,1238 cm⁻¹ ; δ_(H) (250 MHz, CDCl₃ -Me₄ Si) 1.75-1.95 (4H, br m),2.20-2.40 (2H, br m), 2.50 (3H, s), 3.70-3.80 (1H, t), 2.85-2.95 (2H,t), 3.45-3.55 (1H, br m ), 4.30-4.40 (1H, br m ), 7.15-7.30 (5H, br m),M/z 246 (MH⁺ 100% ) (Found: MH⁺ 246.149; C₁₅ H₁₉ NO₂ rquires MH³⁰246.1522).

(B)

rel -(3R*, 3aS*, 7aS*)-3-Benzyl -2-methyl -2,3,3a,4,5,6,7,7a-octahydrobenzo[d]isoxazol-4-one [2.51 g, 102 mMol; preparedas described under (A)] in methanol was stirred at 0° C. and treateddropwise with acetyl chloride (0.73 ml, 102 mMol). The solvents wereremoved in vacuo to yield an oil which became a white foam under highvacuum (0.01 mm Hg). This crude product was recrystallised from acetoneto give the unsubstituted title compound hydrochloride as a whitecrystalline solid, m.p. 154°-156° C. (decomposition) in quantitativeyield.

(C)

N-(2-m-Fluorophenylethylidene)methylamino N-oxide (1.0 g, 4.61 mmol) and2-cyclohexenone (0.5 g, 5.20 mmol) were refluxed in toluene overnightunder nitrogen. Removal of the solvent gave rel -(3R*, 3aS*,7aS*)-3-m-fluorobenzyl -2-methyl2,3,3a,4,5,6,7,7a-octahydrobenzo[d]isoxazol-4-one as a brown oil (341mg, 24%), δ_(H) (400 MHz, CDCl₃ -Me₄ Si) 1.98-2.30 (6H, m), 2.52 (3H,s), 2.72 (1H, m), 2.95-2.98 (2H, br m), 3.51 (1H, br m), 4.40 (1H, brm), 7.41-7.52 (4H, m); δ_(C) (100 MHz, CDCl₃ -Me₄ Si) 19.70, 25.97,29.70, 39.43, 40.54, 45.01, 59.16, 69.62, 76.70, 123.50, 125.47,126.32,128.82, 133.06, 138.82; M/z 314 [(M+H)⁺ 12%](Found: M⁺ 313.1285; C₁₆ H₁₈NO₂ F₃ requires M⁺ 313.1290).

(D)

The procedure described in (C) was repeated usingN-[2-(m-trifluoromethylphenyl)ethylidene]methylamine N-oxide in place ofN-(2-m-fluorophenylethylidene)methylamine N-oxide to provide rel-(3R*,3aS*, 7aS*) -3-m-(trifluoromethyl)benzyl -2-methyl 2,3a4,5,6,7,7a-octahydrobenzo [d]isoxazol -4-one as an oil, δ_(H) (400 MHz,CDCl₃ -Me₄ Si) 1.73-1.84 (6H, m), 2.32-2.36 (1H, m), 2.42 (3H, s),2.51-2.64 (1H, br m), 2.73-2.80 (1H, br m), 3.38 (1H, br s), 4.27 (1H,br s), 6.77-7.16 (4H, m); δ_(C) (100 MHz, CDCl₃ -Me₄ Si) 19.36, 25.65,40.11, 58.71, 69.32, 76.25, 112.95, 113.17, 116.03, 116.25, 125.01,129.43, 129.52, 140.20, 208.86; M/z 264 [(M+H)⁺ 18%](Found: M⁺ 263.1324;C₁₅ H₁₈ NO₂ F requires M⁺ 263.1322).

EXAMPLE 2

Preparation ofrel-(3R*,3aS*,7aS*)-3-benzyl-2-methyl-2,3,3a,6,7,7a-hexahydrobenzo[d]isoxazole

N-(2-Phenylethylidene)methylamine N-oxide (797 mg, 5.34 mmol) and1,3-cyclohexadiene (3 ml) were heated together at 70° C. in a sealedtube under nitrogen for 14 hours. The solution was cooled to roomtemperature and the excess 1,3-cyclohexadiene was removed under reducedpressure to yield a viscous oil (1.07 g, 87%). This crude product waspurified by flash chromatography using 60:40 v/v petroleum ether(fraction of bp 40°-60° C.):ethyl acetate as the solvent system to givethe title compound (Rf=0.34) as a pale yellow oil (375 mg, 35%), υ_(max)(film) 3030, 2920, 2840, 1605, 1495, 1455, 1090 cm⁻¹ ; δ_(H) (400 MHz;CDCl₃ -Me₄ Si) 1.80-2.00 (4H, br m), 2.20-2.25 (1H, m), 2.60-2.65 (3H,s), 2.75-2.95 (2H and 1H, m), 4.20-4.25 (1H, br), 5.6-6.0 (2H, br m),7.20-7.30 (5H, br m); M/z 229 (MH⁺ 100%) (Found: MH⁺ 230.1545; C₁₅ H₁₉NO requires MH⁺ 230.1574).

EXAMPLE 3

Preparation of rel-(3R*,3aS*,7aS*)-2-methyl-3-(2-phenylethyl)-2,3,3a,4,5,6,7,7a-octahydrobenzo[d]isoxazol-4-one

N-(3-Phenylpropylidene)methylamine N-oxide (1.50 g, 9.19 mmol) and2-cyclohexenone (5 ml) were heated at 80°-90° C. for 24 hours in asealed tube under nitrogen. The solution was cooled to room temperatureand the excess 2-cyclohexenone was removed under reduced pressure usingKugelrohr distillation to yield the crude product as a dark yellow oil(2.36 g, 99%). The crude product was purified by flash chromatographyusing 60:40 v/v light petroleum (fraction of bp 40°-60° C.):ethylacetate as the solvent system to give the title compound as a colourlessoil (2.11 g, 89%), υ_(max) (film) 2941, 2872, 1710, 1454, 1235 cm⁻¹ ; υH(250 MHz, CDCl₃ -Me₄ Si) 1.70-2.0 (6H, br m), 2.25-2.55 (2H, m),2.60-2.80 (2H, m), 2.70 (3H, s), 2.75 (1H, t), 3.25 (1H, br m), 4.45(1H, br m) , 7.10-7.30 (5H, br m) ; M/z 259 (M⁺ 100%) (Found: M⁺259.1572; C₁₆ H₂₁ NO₂ requires M⁺ 259.1603).

EXAMPLE 4

Preparation ofCis-2-methyl-2,3,3a,4,4a,5,6,7,7a-octahydrobenzo[d]isoxazol-4-one

(A)

A mixture of sodium acetate trihydrate (13.6 g, 0.1 mmol ), aqueousformaldehyde (37% w/w) (10.0 ml, 0.13 mol ) and 2-cyclohexenone (10.6 g,0.11 mol) in ethanol (80 ml) was vigorously stirred. To this was addedover 90 minutes N-methyl hydroxylamine hydrochloride (8.6 g, 0.1 mol) inethanol (45 ml) containing water (2.5 ml), and the stirring wascontinued overnight. The reaction mixture was then filtered, condensedto half volume under reduced pressure and then neutralised usingsaturated sodium bicarbonate solution. The aqueous solution wasextracted using ethyl acetate (3×75 ml). The combined organic extractswere washed with water (1×30 ml) and dried using saturated sodiumchloride solution (1×50 ml) and magnesium sulphate. Removal of thesolvents in vacuo gave a crude product in the form of a pale yellow oil(9.18 g, 59%). 5.3 g of this crude product was purified by flashchromatography using ethyl acetate as the solvent system to give thetitle compound as a colourless oil (6.86 mg), υ_(max) (film) 3419, 29512872 1709 1671 1456, 1239, 1087 cm⁻¹ ; δ_(H) (250 MHz, CDCl₃ -Me₄ Si)1.90-2.05 (4H, br m), 2.35-2.50 (2H, m), 2.70 (3H, s), 2.80-3.20 (2H and1H, br m), 4.40-4.70 (1H, m); M/z 156 (MH⁺ 100%).

(B)

In a variation of the procedure described under (A) of Example 1 thetitle compound was alternatively prepared by the reaction ofN-(ethylidene)methylamine N-oxide with 2-cyclohexenone. The N-oxide isformed in situ by the tungstate catalysed oxidation of dimethylamine(Na₂ WO₄.2H₂ O/H₂ O₂ / (CH₃)₂ NH in a 1.4:77:35 molar ratio in H₂ O) andreacted for 12 hours at room temperature with a 1.05 molar excess of the2-cyclohexenone. working up by extraction with CH₂ Cl₂, washing with H₂O, saturated aqueous NaHCO₃ and saturated brine, and evaporation gives abrown oil which is purified by flash chromatography as described under(A) above to give the title compound with similar properties to thosedescribed under (A) above.

EXAMPLE 5

Preparation of rel-(3R*,3aS*,7aS*)-3-benzyl-2-methyl 2,3,3a,4,5,6,7,7a-octahydrobenzo[d]isoxazole

N-(2-phenylethylidene)methylamine N-oxide (5.0 g, 33.5 mmol) andcyclohexene (15 ml) were heated at 80° C. for 18 hours in a sealed tubeunder nitrogen. The solution was cooled to room temperature and thecyclohexene was removed under reduced pressure to yield a viscous brownoil (6.5 g, 84%). The crude product was dissolved in hot either (50 ml)and refrigerated. After standing for 48 hours the product was filteredto give the title compound as a white crystalline solid, (1.15 g, 15%).Two further crops were isolated from the washings, (2.37 g, 31%) and(2.05 g, 27%) but these were less pure than the main fraction.

Note

The crude product was alternatively purified by flash chromatographyusing 60:40 v/v light petroleum (fraction of bp 40°-60° C.):ethylacetate to give the title compound (R_(f) =0.31).

EXAMPLE 6

Preparation of rel-(3R,3aS*,7aS*)-3-fur-2-yl-2-methyl-2,3,3a, 4,5,6,7,7a-octahydrobenzo[d]isoxazol -4-one

N-(Fufurylidene)methylamine N-oxide (1.03 g, 9.44 mmol) and2-cyclohexenone (3 ml) were heated at 90° C. for 1 hour. After coolingto room temperature hydroquinone (22 mg) was added and the temperatureraised to 65°-70° C. for 11 hours. The solution was cooled and theexcess 2-cyclohexenone was removed by Kugelrohr distillation underreduced pressure to yield a light brown oil (1 .88 g, 90%). The crudeproduct was purified by flash chromatography using ethylacetate:petroleum ether (bp 40°-60° C.) in a ratio of 3:7 v/v as thesolvent system. The title compound had an Rf of 0.29 and was isolated asa pale yellow oil (1.36 g, 65%), υ_(max) (thin film) 2957, 2877, 1710,1248, 1011 cm⁻¹ ; δH (400 MHz, CDCl₃ -Me₄ Si) 1.67-2.00 (4H, m),2.34-2.38 (1H, m), 2.44-2.49 (1H, m), 2.67 (3H, s), 3.28-3.31 (1H, t),4.20 (1H, br s), 4.67-4.68 (1H, br s), 6.27-6.30 (2H, m), 7.34-7.35 (1H,t); M/z 222 (MH⁺ 100%).

EXAMPLE 7

Tests of Physiological Activity Drugs

The compound of Example 1(A) (hereinafter identified as SP1640) wassuspended in a minimum quantity of polyethylene glycol (PEG) and dilutedwith distilled water. Ondansetron, zacopride, nicotine dihydrogentartrate, cocaine hydrochloride and scopolamine hydrobromide weredissolved in saline. Alcohol was made up as an 8% w/v solution ofethanol in drinking water. Diazepam was dissolved in the minimumquantity PEG and made up to volume with distilled water. All drugs wereadministered in a volume of 1 ml/kg (rat) and 1 ml/100 g (mouse).

(1) Anxiolytic Activity

The compound of Example 1(A) was tested for anxiolytic activity usingthe following procedures.

Studies Using the Black:White Box Test

Naive BKW male albino mice (Bradford bred) 30-35 g were used in allstudies. 10 mice were normally housed in each cage and kept for at leasttwo weeks on a 12 hour light/dark cycle with lights off at 07.00 h.Behavioural testing was conducted between 13.00-18.00h in a darkenedroom illuminated with red light. Nice were taken from the dark holdingroom to the testing room in an enclosed trolley and allowed at least 1hour for adaptation to the new environment.

The apparatus used for the detection of changes in exploratory behaviourconsisted of an open-topped box (45×27×27 cm high) lined into 9 cmsquares, two-fifths painted black and Illuminated under a dim red light(1×60 W) and partitioned from the remainder of the box which was paintedwhite and brightly illuminated with a 60 W light source located 17 cmabove the box. An opening 7.5×7.5 cm located at floor level in thecentre of the partition allowed access between the two compartments. Atthe start of testing mice were placed individually into the centre ofthe white, brightly lit area of the test box.

The mice were observed over a 5 minute period by remote video recordingand four behaviours noted: (i) the number of exploratory rearings in thewhite and black sections, (ii) the number of line crossings in the whiteand black areas, (iii) the time spent in the white and black areas and(iv) the latency of the initial movement from the white to the blackarea. An anxiolytic effect is evidenced by an enhanced preference forthe white area as compared with the black area which is that preferredunder normal conditions.

In initial studies, separate groups of naive mice received the vehicleonly or SP1640 at 1 ng/kg, 1 μg/kg or 1 mg/kg i.p. 60 minutes beforeexposure to the black:white test box. A second study determine a widerdose range (0.1 ng/kg-10 mg/kg). In subsequent studies the oral efficacyof SP1640 was determined over a wide dose range (0.01 ng/kg-1 mg/kg).

Mice were used once only in treatment groups of 5. Results were analysedusing single factor ANOVA followed by Dunnett's t-test for comparingmultiple treatments with a single control.

Studies on Rat Social Interaction

Adult male Hooded-Lister rats (Bradford bred) 225-275 g were housed ingroups of five and kept on a 12 hour light/dark cycle with lights on at07.00 h. Tests were conducted between 13.00-18.00 h in an illuminatedroom following a period of adaptation.

The apparatus used for the detection of changes in rat socialinteraction and exploratory behaviour consisted of an open-toppedperspex box (51×51×20 cm high) with 17×17 cm areas marked on the floorof the box. Two naive rats, from separate housing cages, were placedinto the box (with 2×60 W bright white illumination above) and theirbehaviour observed over a 10 minute period by remote video recording.Two behaviours were noted (i) social interaction between the animals wasdetermined by timing (s) sniffing of partner, crawling under or climbingover partner, genital investigation of partner, following partner and(ii) exploratory locomotion was measured as the number of crossings ofthe lines marked on the floor of the test box.

Separate groups of rats received vehicle or SP1640 (0.1 ng/kg-10 mg/kgi.p.) 40 minutes before testing.

Naive animals were used once only in drug treated pairs in treatmentgroups of 6-8 pairs. Data obtained were analysed using single factorANOVA followed by Dunnett's t-test.

Maintenance of Effects on Long-Term Treatment And Consequences ofWithdrawing from Long-Term Treatment

These studies used the mouse black:white box. Mice received SP1640 1ng/kg i.p. b.d. or 1 mg/kg i.p. b.d. for 14 days and the treatments wereabruptly withdrawn.

Separate groups of mice were tested on days 3, 7 and 14 of treatment andthen 8, 12, 24, 48 and 96 hours after the last dose.

Mice were used on one occasion only in groups of 5. Data obtained wereanalysed using single factor ANOVA and Dunnett's t-test whereappropriate.

Assessment of Ability to Cross-Tolerate with Diazepam

These studies used the mouse black:white box model. Mice were treatedwith diazepam 10 mg/kg i.p. b.d. for 7 days and the treatment was thenabruptly withdrawn. The withdrawal phenomena which characteristicallyresult following the abrupt cessation of diazepam treatment are maximal24 hours after the last dose of diazepam. SP1640 (1 μg/kg i.p. b.d.) wasgiven to separate groups of mice during the period of withdrawal todetermine the ability to prevent the development of withdrawalphenomena.

Mice were used on one occasion only in groups of 5. Data obtained wereanalysed using single factor ANOVA and Dunnett's t-test whereappropriate.

Ability to Inhibit the Behavioural Consequences of Withdrawing FromDrugs of Abuse

Following long-term treatment of mice with alcohol (8% w/v in thedrinking water for 14 days), nicotine (0.1 mg/kg i.p. b.d. for 7 days)or cocaine (1 mg/kg i.p. b.d. for 14 days) and abrupt withdrawal oftreatment, mice (tested in the black:white box) exhibited markedbehavioural changes which were maximal. 24 hours after cessation oftreatment. The ability of SP1640 to prevent the development of thesebehavioural changes was determined when SP1640 1 μg/kg i.p. b.d. wasgiven to mice during the 24 hour period of withdrawal, the last dose 40minutes prior to behavioural testing.

Mice were used once only in treatment groups of 5. Data obtained wereanalysed using single factor ANOVA and Dunnett's t-test whereappropriate.

RESULTS

The results obtained in the various tests for anxiolytic activity wereas follows.

Studies in the Black:White Test Box

In initial studies SP1640 was administered to mice via theintraperitoneal route at a dose of 1 ng/kg, 1 μg/kg or 1 mg/kg. SP1640produced changes in behaviour indicative of an anxiolytic potential at 1ng/kg, 1 μg/kg and 1 mg/kg. In a second study using a dose range of 0.1ng/kg to 10 mg/kg SP1640 produced changes in behaviour indicative ofanxiolysis over the range of 1 ng/kg-10 mg/kg. The results of the secondstudy are set forth in FIG. 1 (in this and subsequent figures the symbolV (vehicle) or the symbol C (control) indicate the control in which onlythe vehicle was used without compound).

In subsequent experiments the oral efficacy of SP1640 was establishedand full 1 dose response curves constructed.

SP1640 was effective to induce anxiolysis following oral administrationover a wide dose range (100 ng/kg-1 mg/kg). The results are set forth inFIG. 2.

At none of the doses of SP1640 tested was there any suggestion of thedevelopment of sedation.

Studies on Rat Social Interaction

SP1640 was administered intraperitoneally at doses of 0.1-10 mg/kg.SP1640 increased rat social interaction at 1 ng/kg-10 mg/kg (FIG. 3).SP1640 did not cause changes in locomotor activity at any of the dosestested. The results are set forth in FIG. 3.

Maintenance of Effects on Long-Term Treatment and Consequences ofWithdrawing From Long-Term Treatment

During long-term treatment with SP1640 (1 ng/kg i.p. b.d. and 1 mg/kgi.p. b.d.) the anxiolytic profile of responding was maintained whentested on days 3, 7 and 14 of treatment, the results being set forth inFIGS. 4 and 5. Following abrupt cessation of treatment there was noindication of the development of anxiogenesis; rather, the anxiolyticprofile was maintained for up to 12 hours (SP1640 1 ng/kg, FIG. 4) or 48hours (SP1640 1 mg/kg, FIG. 5).

Assessment of Ability to Cross-Tolerate with Diazepam

The anxiolytic effect of diazepam given for 7 days is seen from FIG. 6.24 hours after cessation of treatment the anxiolytic profile hadreversed to an anxiogenic profile of responding.

SP1640 (1 μg/kg i.p. b.d.) given during the period of withdrawalprevented the development of withdrawal anxiogenesis and induced ananxiolytic profile of responding. The results produced are set forth inFIG. 6.

Ability to Inhibit the Behavioural Consequences of Withdrawing FromDrugs of Abuse

Alcohol (8% w/v) in drinking water for 14 days induces behaviouralchanges indicative of anxiolysis, within 24 hours of withdrawing alcoholfrom the drinking water mice displayed a profile of activity indicativeof anxiogenesis.

SP1640 (1 μg/kg i.p.) prevented the development of withdrawalanxiogenesis. The results are set forth in FIG. 7.

Nicotine (0.1 mg/kg i.p. b.d.), administered for 7 days, also inducedbehavioural changes indicative of anxiolysis. Within 24 hours ofwithdrawing nicotine treatment profile of activity indicative ofanxiogenesis was apparent. SP1640 (1 μg/kg i.p. b.d.) prevented thedevelopment of withdrawal phenomena when given during the period ofwithdrawal. The results are set forth in FIG. 8.

In a similar way to alcohol and nicotine, cocaine (1mg/kg i.p. b.d.),administered for 14 days, produced changes in responding indicative ofanxiolysis which, following a 24 hour period of withdrawal, reverted toa profile of anxiogenesis.

SP1640 (1 μg/kg i.p. b.d.) prevented the development of withdrawalphenomena when given during the period of withdrawal. The results areset forth in FIG. 9.

(2) Improvement of Learning and Reversal of Scopolamine-Induced Amnesia

The compound of Example 1(A) (SP1640) was tested at sub anxiolyticdoses.

The following procedure was employed:

Mouse Habituation Test

The studies used male albino (BKW) mice initially weighing 27-35 g(young adult mice of 6-8 weeks) or 40-45 g (aged mice of 9 months). Intheir home room mice were housed in groups of 10 and were given freeaccess to food and water. The mice were kept at a 12 hour light and 12hour dark cycle with lights off at 7.00 a.m. and on at 7.00 p.m.

The test apparatus consisted of an open-topped box (45×27×27 cm) onethird painted black and illuminated under a dim red light (1×60W) andpartitioned from the remainder of the box which was brightly illuminatedwith a 100 W light source located 17 cm above the box. Access betweenthese two areas was enabled by means of a 7.5×7.5 cm opening located atfloor level in the centre of the partition (which also served to preventdiffusion of light between the two compartments of the test box). Thefloor area was lined into 9 cm squares.

The habituation test was carried out daily by placing mice in the centreof the white section of the test box (mice taken from dark homeenvironment in a dark container, to the experimental room maintained inlow red lighting, and would normally be averse to the bright whiteconditions). Testing was carried out between 8.30 a.m. and 12.30 p.m.The test period was 5 minutes per day. Behaviour was assessed via remotevideo recording, and the following measurements taken:

1. Latency to move from the white to the black section (sec).

2. Numbers of exploratory rears in the white and black sections duringthe 5 minute tests.

3. Numbers of line crossings (exploratory locomotion) in the white andblack sections during the 5 minute test.

4. % Time spent in the black section of the box during the 5 minutetest.

5. Numbers of transitions between the black and white sections of thetest box during the 5 minute test (since this parameter was not changedin any situation in the present studies, data for transitions is notgiven or commented on further).

On repeated daily exposure to the box young adult mice habituate to thetest situation by moving rapidly into the black area where they spendmost time and exhibit most behaviour (measured as exploratory rears andcrossings of lines marked on the test box floor). Generally, for youngadult mice the habituation process occurs over a 4-6 day period and, forexample latency for the initial movement from the white to the blacksection is reduced from initial values of 10-12 seconds to 1-4 secondsby the 5th-6th day of test.

In the contrast to the findings with young adult mice (6-8 weeks old),aged mice (9 months old) fail to habituate to the black:white testsystem. From the first day of test aged animals' behaviour appears to beequally distributed between the white and black sections, and expectedchanges in behaviour to favour the preferred black environment do notoccur.

The habituation profile of young mice was disrupted by acute scopolamine(0.25 mg/kg i.p., 40 minutes before test) (dose carefully selected asminimally effective, without interference from peripheral effects aschecked by assessments of the actions of the same dose ofmethylscopolamine). Aged mice were found to be particularly sensitive toscopolamine and they were challenged with the maximally tolerated doseof 0.1 mg/kg (40 minutes before test). SP1640 was given i.p. b.d.throughout the habituation period (dose of 0.1 ng selected as notinterfering with anxiety response). Injections of the compound were at8.00 a.m. (40 minutes before testing) and 6.00 p.m.

The results are set forth in FIGS. 10 to 16 of which FIGS. 10 and 11illustrate the ability of SP1640 to improve basal inhibition in youngadult mice (FIG. 10 being the control), FIGS. 12 and 13 illustrate theability of SP1640 to improve basal inhibition in aged mice (FIG. 12being the control), and FIGS. 14, 15 and 16 illustrate the ability ofSP1640 to prevent the impairment in habituation caused by the acute orchronic scopolamine challenge (FIGS. 14 and 15 being the controls).

We claim:
 1. A method of treatment of a patient requiring improvement oflearning disability and/or reversal of amnesia which comprisesadministering to said patient a therapeutically effective amount of acompound of formula (I) ##STR7## in which R₁ represents hydrogen, a C₁₋₆aliphatic hydrocarbyl group or a C₁₋₄ aliphatic hydrocarbyl groupsubstituted by a C₃₋₆ alicyclic hydrocarbyl group or by a phenyl group,which phenyl group is unsubstituted or substituted by a halogeno or C₁₋₃halogenoalkyl group, R₂, represents hydrogen, R₃ represents hydrogen, a5- or 6-membered ring aromatic heterocyclyl group containing one or twoheteroatoms selected from nitrogen, oxygen and sulphur which isunsubstituted or substituted by a halogeno or C₁₋₃ halogenoalkyl group,or a group AR wherein A is a straight chain C₁₋₄ aliphatic hydrocarbylgroup terminally substituted by R which is hydrogen, a phenyl group or a5- or 6-membered ring aromatic heterocyclyl group containing one or twoheteroatoms selected from nitrogen, oxygen and sulphur, which phenyl orheterocyclyl group R is unsubstituted or substituted by a halogeno orC₁₋₃ halogenoalkyl group, R₄ and R₅ each represent hydrogen or togetherrepresent an oxo group and R₆, R₇ and R₈ each represent hydrogen, or R₄represents hydrogen arid two of R₅, R₆, R₇ and R₈ together represent thesecond bond of a double bond joining positions 4 and 5, 5 and 5 or 6 and7 with the remaining two of R₅, R₆, R7 and R₈ representing hydrogen, thecompound optionally being in the form of a salt thereof formed with aphysiologically acceptable inorganic or organic acid.
 2. A method forthe treatment of a patient requiring improvement of learning disabilityand/or reversal of amnesia which comprises administering to said patienta therapeutically effective amount of a compound of the formula (I)##STR8## in which R₁ represents hydrogen, a C₁₋₆ aliphatic hydrocarbylgroup or a C₁₋₄ aliphatic hydrocarbyl group substituted by a C₃₋₆alicyclic hydrocarbyl group, R₂ represents hydrogen, R₃ representshydrogen or a group AR wherein A is a straight chain C₁₋₄ aliphatichydrocarbyl group terminally substituted by R which is hydrogen or aphenyl group which is unsubstituted or substituted by a trifluoromethylgroup, R₄ and R₅ each represent hydrogen or together represent an oxogroup and R₆, R₇ and R₈ each represent hydrogen, or R₄ representshydrogen and two of R₅, R₆, R₇ and R₈ together represent the second bondof a double bond joining positions 4 and 5, 5 and 5 or 6 and 7 with theremaining two of R₅, R₆, R₇ and R₈ representing hydrogen, the compoundoptionally being in the form of a salt thereof formed with aphysiologically acceptable inorganic or organic acid.
 3. A methodaccording to claim 3, in which R₁ is a C₁₋₆ alkyl group.
 4. A methodaccording to claim 2, in which R₁ is methyl.
 5. A method according toclaim 2, in which R₃ is hydrogen.
 6. A method according to claim 2, inwhich R₃ is C₁₋₄ alkyl group.
 7. A method according to claim 2, in whichR₃ is a C₁₋₄ alkyl group substituted by an unsubstituted phenyl group.8. A method according to claim 2, in which R₃ is a benzyl or2-phenylethyl group.
 9. A method according to claim 2, in which R₄ to R₈are each hydrogen.
 10. A method according to claim 2, in which R₄, R₇and R₈ are each hydrogen and R₅ and R₆ are the second bond of a doublebond joining positions 4 and
 5. 11. A method according to claim 2, inwhich R₄ and R₅ are an oxo group and R₆, R₇ and R₈ are each hydrogen.12. A method according to claim 2, wherein the compound of formula (I)is cis-2-methyl-2, 3, 3a, 4, 5, 6, 7,7a-octahydrobenzo[d]benzoisooxazol-4-one.
 13. A method according toclaim 2 wherein the compound of formula (I) is cis-2-methyl-2, 3, 3a, 6,7, 7a-hexahydrobenzo[d]isoxazole.
 14. A method according to claim 2wherein the compound of formula (I) is cis-3-benzyl-2-methyl-2, 3, 3a,4, 5, 6, 7, 7a-octahydrobenzo[d]isooxazol-4-one.
 15. A method accordingto claim 2 wherein the compound of formula (I) iscis-3-benzyl-2-methyl-2, 3, 3a, 6, 7, 7a-hexahydrobenzo[d]isoxazole. 16.A method according to claim 2 wherein the compound of formula (I) iscis-2-methyl-3-(2-phenylethyl)-2, 3, 4, 5, 6, 7,7a-octahydrobenzo[d]isoxazol-4one.
 17. A method according to claim 2, inwhich a group R₃ which is not hydrogen is in the trans configurationrelative to the hydrogen atoms at positions 3a and 7a.
 18. A methodaccording to claim 14, in which a group R₃ which is not hydrogen is inthe trans configuration relative to the hydrogen atoms at positions 3aand 7a.
 19. A method according to claim 15, in which a group R₃ which isnot hydrogen is in the trans configuration relative to the hydrogenatoms at positions 3a and 7a.
 20. A method according to claim 16, inwhich a group R₃ which is not hydrogen is in the trans configurationrelative to the hydrogen atoms at positions 3a and 7a.